Forests at different latitudes

Forests account for 75% of the gross primary production of the Earth’s biosphere, and contain 80% of the Earth’s plant biomass. Net primary production is estimated at 21.9 gigatonnes carbon per year for tropical forests, 8.1 for temperate forests, and 2.6 for boreal forests.[7]

Forests at different latitudes and elevations, and with different precipitation and evapotranspiration[9] form distinctly different biomes: boreal forests around the North Pole, tropical moist forests and tropical dry forests around the Equator, and temperate forests at the middle latitudes. Higher elevation areas tend to support forests similar to those at higher latitudes, and amount of precipitation also affects forest composition.

Almost half the forest area (49 percent) is relatively intact, while 9 percent is found in fragments with little or no connectivity. Tropical rainforests and boreal coniferous forests are the least fragmented, whereas subtropical dry forest and temperate oceanic forests are among the most fragmented. Roughly 80 percent of the world’s forest area is found in patches larger than 1 million hectares. The remaining 20 percent is located in more than 34 million patches across the world – the vast majority less than 1 000 hectares in size.[10]

Human society and forests influence each other in both positive and negative ways.[11] Forests provide ecosystem services to humans and serve as tourist attractions. Forests can also affect people’s health. Human activities, including unsustainable use of forest resources, can negatively affect forest ecosystems.[citation needed]